Tyson Research Center

 Tyson Research Center Weather Station - General Information

Elevation: 174 meters (570 feet)
Date Installed: October 2, 2000

Equipment:

Datalogger: Campbell Scientific CR10x.
Storage Module: SM4M module, capacity 2 million data values.
Temperature: Vaisala HMP45C with platinum resistance detector.
Relative Humidity: Vaisala Humicap 180 capacitive sensor.
Anemometer: Climatronics CS800L wind speed and direction.
Raingage: Met One 385AC tipping bucket rain or snow gage, heated.
Second Raingage: Belfort "Universal" or standard collector-type gage.
Pyranometer: Licor LI200X radiation sensor, silicon detector.
Barometer: CS105 Sensor, recording in mm Hg.
Tower: Universal UT30, 10 meters (33 feet), with lightning rod.
Power: PS12LA 12-volt with charging regulator.

Program and Measurements: samples air temperature (degrees C), relative humidity (%RH), wind speed (MPH), wind direction (0-360 degrees), atmospheric pressure (mm Hg) and solar radiation (KW per square meter), every 1.0 second. Average values are recorded at 10-minute and 60-minute intervals. Also records maximum and minimum wind speed values. Precipitation is recorded in 0.01 inch increments.

The weather station is situated in a large, relatively flat field, so that trees do not interfere with wind currents, solar radiation, or other weather measurements. This area is typical of the Tyson Research Center and its oak-hickory forest with interspersed grassy clearings. A white weather shelter house contains a hi-lo "backup" thermometer.

The electronic weather station includes a Campbell Scientific CR10X datalogger, SM4M storage module, regulated 12-volt power supply, and various sensors. Data from the storage module is downloaded about once a week. Future equipment may include soil moisture sensors, or a modem to allow remote access and "real-time" download of data.

The tower is made of aluminum, and is 10 meters (33 feet) tall. It is anchored in concrete 4 feet deep, and at the top is a lightning rod to protect the weather instruments in case of a lightning strike. The tower has 3 guy wires to help support it, and is hinged at the bottom so that the instruments at the top of the tower can be easily lowered close to the ground for maintenance or calibration.

Wind Speed:

The instrument at the top of the tower, with 3 spinning cups, records wind speed. It has a low starting threshold (< 1 MPH), and records wind speeds ranging from 0-125 MPH. Measurements are taken every 1 second, with 10-minute and 1-hour averages being recorded, along with maximum wind speeds.

Wind Direction:

The vane located at the top of the tower measures wind direction. It is coupled to a precision low-torque potentiometer. Direction measurements range from 0 to 360, corresponding to degrees in a circle or compass points. 0 (and 360) = north, 90 = east, 180 = south, and 270 = west. Wind direction is measured by recording the direction the wind is coming from.

The small sensor located on an arm extending out horizontally from the tower measures solar radiation. This instrument senses changes in sun intensity with a photovoltaic detector. It is located on the south side of the tower, so tower poles do not cause shadows to fall on the sensor at any time of the day.

This essential parameter is measured with a platinum resistance temperature detector, a very small and sensitive instrument. It is located inside a white 12-plate radiation shield, to protect the instrument from direct sunlight. It is located at a height of 2 meters (approx. 6 feet) to avoid temperature extremes found near ground level.

Relative humidity is the amount of water vapor that can be held in the air at a given temperature. It is expressed in percent, ranging from 0% (very dry) to 100% (dripping wet). The relative humidity sensor is also located inside the white 12-plate radiation shield, to protect the instrument from direct sunlight.

An atmospheric pressure sensor or barometer was added to the weather station in April 2002. It is a CS105 Barometric Pressure Sensor, Model PTB101B from Vaisala.

A MetOne gage measures rain or snow water equivalent on a continuous basis. The gage contains an electric heater which automatically melts hail, ice or snow that falls into the gage. A mercury switch is located in the gage which sends an impulse to the datalogger, with each tip or 0.01 inch of precipitation.

"Backup" raingages are also present at the weather station. A second gage is a Belfort "Universal" or standard collector-type gage.

Precipitation is expressed in inches per year, utilizing a "calendar year." Another important factor in measuring precipitation, is intensity, or amount of rain per time unit. For example, one inch of rain in 10 minutes is much more "intense" (heavy) than the same amount in a 24-hour period.